Sampling switch



Feb. 19, 1963 M. FRIEDMAN ETAL SAMPLING SWITCH Filed Juy 2o, 1960| 3Sheets-Sheet 1 INVENTORS PI/IILTDN FRIE MEN RVINE P. f aasmY VM/WW 5159klit-)63 w1. smlEmMwN En-,AL @018,355

- :swam: ,suman mima .am ,29, .1969

y @ooo 6011*::12- 12151 \yi/ INVENTUM MzLmN Frust-)MEN 5 Imz'mr: P. Mn-Smy- United States Patent O 3,673,356 SAIs/@LENG SWHCH Mitten Friedman,Roslyn, and trying il. Magasiny, Philadelphia, Pa., assignors toSclraevitz Engineering, a corporation or New .lersey Filed duly Ztl,196i), Ser. No. 44,0% 2 Claims. (El. Zitti-24) numerous other functionsare often necessary. Such a telemetering system generally includestransducers which convert each variable quantity to be measured into acorresponding electrical signal. The electrical signals from thetransducers may then be used to modulate subcarrier oscillators, codingdevices and transmitters directly. The electrical signals may also berecorded on magnetic tape or other suitable means. The output signalfrom the coding device or sub-carrier oscillators or other devices asthe case may be may, in turn, be used to modulate the carrier signal ofa high frequency transmitter. A carrier signal transmitted from thetransmitter in a guided missile, for example, may then be received by areceiving station on the ground or other remote point. Suitabledemodulation means are employed to restore the electrical signalsoriginating at the transducers. Since these electrical signals arefunctions of the variable quantity measured, indications of thecharacter of the measured functions are readily attainable.

in order to utilize available bandwidth to its greatest extent,especially Where the amount of desired information is great and theavailable bandwidth is relatively small, it is desirable to usemultiplexing circuits. The use of multiplexing circuits permits the useof so'called time division or frequency division methods to impress anumber of information signals upon a single carrier signal.

A time division system may utilize a single coding channel, such as apulse code modulator, a pulse amplitude to pulse width modulator or asub-carrier oscillator associated with a plurality of transducers withthe electrical outputs from the transducers periodically sampled. Thistime division method permits a maximum amount of information utilizing asingle code channel. ln carrying out such time division methods,mechanical switching devices or commutators are often used since theyare relatively simple and oder a maximum amount of economy andreliability.

Among the major problems encountered in mechanical commutators have beenthe relatively high degree of brush wear. Much of this brush Wear isrelated to high speed operation and occurs when a brush makes and breakscontact with electrical contacts which are generally disposed atdifferent surface levels With respect to the insulated plate with whichthe contacts are generally associated.

Another problem sometimes encountered in the manu- Cil facture ofmechanical commutators has been the amount of soldering and electricalconnections which must be made in wiring a large number of contacts toappropriate circuitry. Such wiring is not only expensive and timeconsuming, but also increases the likelihood of defects within a systemresulting from defective electrical connections.

It is known that mechanical commutators must often be designed for aparticular application. The reasons for this are that the number ofsources to be sampled may be different having different impedances orsignal levels, Various phasing problems may be more critical in someapplications than others, and for various other reasons. Standard partseasily adaptable for use in building a wide variety of different typesof commutators for different applications would be highly desirable.

it is an object of this invention to provide a novel switching device inwhich brush wear is minimized.

It is a further object of this invention to provide an improvedswitching device for sampling a plurality of signal sources in which thewiring required in manufacturing such as a switching device isminimized.

It is still a further object of this invention to provide an improvedtype of sampling switch which may be readily assembled in a variety offorms and congurations using similar type parts.

lt is still a further object of this invention to provide an improvedswitching device having long life, low move generation, a minimum amountof thermoelectric effects and low contact resistance.

In accordance with the present invention, `a device is provided whichmay be used in sequentially sampling or decommutating electricalsignals. A plurality of brush elements is disposed to electricallyengage one or more contacts. The brush elements or the contacts aredisposed in an offset or staggered relationship with respect to theother. Means for relatively moving the brush elements and the contactswith respect to each other are provided. A different brush elementelectrically engages one or more contacts at diiierent time intervals.Additional means, which may include another brush and contact, areprovided for connecting the sampled signals to an output circuit.

Other objects and advantages of the present invention will be apparentand suggest themselves to those skilled in the art to which the presentinvention is related, from a reading of the following specication andclaims, in conjunction with the accompanying drawings, in which;

FlGURE l is an elevational view, partly in cross section illustrating asampling switch, in accordance with the present invention;

FGURE 2 is a view taken along lines 2-2 oi FlG- URE l FIGURE 3 is a Viewlooking downward on a brush holder illustrated in PiGURE l;

FlGURE 4 is an elevational View, partly in cross section, illustratinganother form of sampling switch, in accordance with the presentinvention;

FIGURE 5 is an isometric view illustrating in greater detail the drummember of FIGURE 4;

FIGURE 6 is a front View illustrating in somewhat greater detail thebrush holder assembly of FIGURE 4;

FIGURE 7 is a front view illustrating various parts which may beemployed in assembling ano-ther form of sampling switch, in accordancewith the present invention;

FEGURE 8 is a front view illustrating a drum member comprising thevarious parts of FIGURE 7 in an assen1- bled form;

FIGURE 9 is a view of a brush holder assembly which may be employed inconjunction with the drum member illustrated in FlGURE 8;

FlGURE l is a view illustrating the drum member of FIGURE 8 and thebrush holder of FIGURE 9 in operative positions with respect to eachother, and

FIGURES l1 and l2 illustrate a drum member and brush assembly,respectively, which may be incorporated into still another form of thepresent invention.

Referring particularly to FEGURES l, 2 and 3, a commute-ter or samplingswitch 2l-il includes drum member 22, made of suitable insulatingmaterial, having a plurality of rings 23 and a ring itl secured thereto.The drum member 22 is connected to a shaft 24, which is rotatablymounted to a frame member 26. A motor 2S is connected to drive the shaft24 and the drum member 22 through a gear reduction mechanism Sil. Themotor a8 may be disposed inside the drum member 22 if space requirementsare critical.

A brush holder 32 is suitable mounted to the frame member and includesan assembly of spring loaded brushes 34. The springs providing the forcemay be of the constant force type. A brush Siti is the last disposedbrush in the assembly, although it may be disposed anywhere along theassembly. The brushes 34 are disposed to engage the rings 23 and thebrush 35 is disposed to engage the ring When the drum member 22 isrotated by the motor 2u, the brushes 34 and 36, being maintained undertension by a group of springs, such as a spring 33, frictionally engagethe rings 23 and fait?.

In a preferred embodiment of the invention, each of the rings 23 maycomprise suitable insulating material with the exception of the ring ttlwhich may be metal or other suitable type of conductive material. Eachof the rings 23 include a relatively small electrically conductiveContact, such as a contact 152, which extends through the drum member 22and adapted to be connected to other electrical circuitry. if deisred,the rings 23 may be made of metal having a portion cut away so that thecontacts are insulated from the main body of the rings. The contacts 'l2are in a staggered relationship with respect to each other so that onlyone of the contacts l2 engage any one of the brushes 34 at any one timewith each of the brushes engaging a corresponding Contact once perrevolution of the drum member. rthe contacts d?. are electricallyconnected to each other and to the solid conductive ring itl by a wireor other conductive means within the drum, as illustrated by a dottedline When the motor 23 is actuated, the drum member 22 is rotated andeach of the contacts l2 sequentially engages` one of the respectivebrushes Se thereby electrically connecting the engaged brush through theconductive means d and the solidconductive ring lil to the brush 3d.

ln operation, a plurality of electrical signal sources may be connectedto the brushes 34 through suitable connectors illustrated by arrows 46.An output signal from the brush 36 may be applied to a utilizationcircuit (not shown) through a suitable connector illustrated by an arrow45S.

When the drum member 22 is rotated, each of the con- -tacts l2sequentially engages one at a time a respective brush 34. Outputelectrical signals from various signal sources connected to the brushes34 are therefore sampled each time the drum member 22 is rotated withthe sampled signals being applied to the utilization circuit through theconnector 4S. The time of the sampling interval is dependent upon thetime interval during which a particular brush is in electricalengagement with a contact. Sampling or switching devices forsequentially sampling a plurality of signal sources and applying the lsampled output signals to a utilization circuit are well known.

During the rotation of the drum member 22, the rings 23 and lotrictionally engage the brushes and 35. Constant tension springs Sti areprovided to produce constant pressure and to minimize the tendency ofthe brushes to bounce or move away from the drum upon hitting anirregularity or rough spot thereon.

in sampling devices used heretofore, considerable brush wear occurredwhen the brush made or broke contact with segmented conductive contacts.The reason for this is that, regardless of the care taken inmanuacturing of the commutato-r plates, it is extremely difticult tohave the various contacts on exactly the same plane as the insulatingmaterial between the contacts. Even printed circuits fail to provide aperfectly flush commutator plate wherein the uneven surfaces betweencontacts and the insulating material do not affect brush wear. Thepresent invention has minimized this problem relating to brush wearcaused by uneven surfaces between the insulating material and thecontacts by minimizing the number of times which a brush makes andbreaks with its associated contact.

While the present invention may sometimes involve the use of a greaternumber of brushes than found in some conventional commutators,nevertheless, the life of the commutator before brush replacement isnecessary enhances in a relationship corresponding to the number ofbrushes employed. Furthermore, in many types of equipment, long life ofthe commutator without excessive replacement and maintenance is oftenmore important than the use of a greater number of brushes. This isespecially true in many types of government equipment involving a largenumber of measurements in a telemetering system associated with amissile, for example.

The insulated portions of the rings 23 should preferably be a materialwhich has a relatively low coeihcient of friction with respect to thebrush material to further minimize the wear ot the brushes. Varioustypes of insulated material such as Bakelite, Kel-F, Tellen or variousplastic compositions may be employed. The brushes may be preferably ofcarbon, silver, graphite or other suitable conductive low frictionmaterial. The contacts including the solid ring may be copper, silver orother type of suitable conductive material.

Referring particularly to FlGURE. 4, another form of the presentinvention includes a drum member Sil suitably connected to be driven bya shaft 52. The shaft 52 is rotatably mounted on bearings to a frame Amotor 5o is mechanically connected through a gear mechanism 5S to rotatethe shaft 52 and, consequently, the drum member 5G.

The drum member Sti, more clearly illustrated in FIG- URE 5, comprises adrum of insulated material having a conductive strip dit extendinglongitudinally along the drum Sil and a conductive strip or ring 62 extoding around the periphery of the drum. The strip 6o is electricallyconnected directly -to the ring r:This arrangement provides a highlyuseful purpose, since eX- tensive wiring may be eliminated, as will beSeen.

A cylindrical brush holder ell is suitably mounted to the frame 54 andis disposed around the drum The brush holder dit includes a plurality ofapertures dis posed in staggered relationship around the peripherythereof. The apertures are adapted to receive a plurality of brushes doand d. The brushes 66 and o3 are spring loaded to continuously engagethe insulated or conductive portions of the drum Sil.

In operation, when the drum do is rotated, the strip ou sequentiallyengages one at a time all of the brushes 66. The brushes d6 may beconnected to a plurality of signal sources by means of input connectors72 (FEGURE 6). The brush 68 continuously engages the ring 62 and isconnected to an output connector 74, which in turn, may

. be connected to a utilization circuit, such as a transmitter in atelemetering system.

The arrangement illustrated in FIGURE 4 is somewhat similar in functionto the arrangement illustrated in FIG- URE l. Oneof the main differencesbetween FIGURES 1 and 4 is that the arrangement of FIGURE l involves thestaggering of the individual contacts with the brushes being disposed ina straight line, whereas, the arrangement of FIGURE 4`involves thestaggering of the brushes with the contact being in a straight line.

The embodiment of FIGURE 4 utilizes the conductive strip 6l) which makesit possible to eliminate the necessity of connecting small individualcontacts by wiring or other means to the output conductive ring. Whenthe drum member 50 is rotated, each of the brushes 60 makes and breakswith the conductive strip 64)z once per revolution. As was pointed outin connection with FIGURE 1, most brush wear and noise occurs as aresult of the brushes bouncing when engaging and disengaging a contactor segment a relatively large number of times during operation, suchwear resulting from the planar irregularities existing between thecontacts and the insulating material. Thus the arrangement of FIGURE 4also provides the advantage of minimum brush wear and consequently, longcommutator life with a minimum amount of maintenance or replacement ofparts.

The bnush holder 64 may be made of insulating material, although this isnot absolutely necessary if insulation between the brushes wereotherwise provided.

In FIGURES 1 and 4, it was illustrated that either brushes or contactscould be staggered while the other was in a relatively straightalignment. Other arrangements which combines these features in a varietyof ways are within the scope of this invention. For example, it may bedesirable to stagger some of the brushes with some of the contactsaligned, and vice versa.

Referring particularly to FIGURES 7 and 8, a number of separate pieceswhich may be made into a drum assembly 76 is illustrated. In FIGURE 7, aplurality of similar type conductive rings 78 are disposed between aplurality of round insulated members l each having a strip orelectrically conductive contact 82.

All the insulated members Si) and the conductive rings 78, being ofsubstantially the same type, may be produced eiliciently in massquantities. In assembling the rings 78 and the members Sil, the contacts82 may be staggered with respect to each other. The assembly 76 may beemployed with a brush holder S4 which includes a plu rality of brushes'86. The brush holder 36 is illustrated in FIGURE 9.

The brushes 86 are divided into groups of three, with each of thebrushes within each group disposed to engage one of the contacts 82 otthe assembly 76. FIGURE 10 illustrates the brush $6 of the holder 84 inengagement with the assembly 76.

The conductive rings 7S electrically connect the contacts 32 to eachother and to a last ring 86 which may be the take oli ring connected toa brush d3. The brush 3S, in turn, may be connected to a utilizationcircuit.

In this embodiment, a commutator or sampling switch involving a varietyof different forms may be constructed using the same type parts. Variousphase relationships between the contacts 82 may be readily adjusted bymerely changing the angular positions of the contacts with respect toadjacent contacts.

It desired, the contacts 32 may be made relatively narrow so as toengage only a single brush. In this case, the insulated members @il maybe made relatively narrow. If this is done, an arrangement somewhatsimilar to the arrangement of FIGURE 1 would result, except that theconductive rings 73 of FIGURE 7 would take the place of the conductivewire connected between the contact segments of FIGURE 1.

Also, if desired, a greater number than three brushes per group may beemployed and the contacts 82, and the insulated member Btl may be madewider. 'Ihe particular arrangement used will depend largely upon theparticular application involved, space requirements, number ot sourcesto be sampled and various other factors.

Referring to FIGURES l1 and 12, there is illustrated still anotherembodiment of the present invention. A drum member 9i) is illustrated inFIGURE ll and a brush holder 92, which may be associated with the drummember during operation, is illustrated in FIGURE 12.

vThe drum member 9@ includes a solid electrically conductive contact 94extending in a helical direction around the surface of the drum member.A conductive slip ring 96 is integrally connected to the helical shapedcontact 94 and extends around the periphery of the drum member 9i).

The brush holder 92 includes a pluarlity of input brushes 9S and anoutput brush lili). The brushes 98 and 1(10, while aligned with respectto each other, are disposed at an angle with respect to the drum member9i).

In operations, the drum member 9i) and the brush holder 92 may besuitably mounted with respect to each other in substantially the samemanner as illustrated and described in connection with FIGURE l. Thedrum member 90 may be rotated with the helical shaped con tact engagingone at a time one of the brushes 9S and contacting all of the brushes 98once for each revolution of the drum member. The brushes 98 are offsetat a slight angle so that they are in proper alignment when engaging thecontact 94. The brush 10G continuouslyr engages the ring 96 duringoperation. Consequently, a plurality of signal sources connected to theinput brushes 9S may be sampled and applied to a utilization circuitthrough the output brush 100.

Again, as in FIGURE 1, each of the brushes 98 engage a contact only onceper revolution of the drum member. Therefore, the wear of the brushes 98is minimized for reasons previously discussed. The solid helical contact94 elminates the necessity of wiring a large number of contactstogether, asin FIGURE l.

While several embodiments have been illustrated, it is evident that thepresent invention may take a wide variety of different forms dependentupon the particular application involved. While drums have beenillustrated, it is conceivable in some applications that a flat circularplate or even a rectangular plate with a reciprocating brush movementmay be employed. The particular sizes and shapes of the brushes andcontacts may be different than those illustrated. Numerous differenttypes of insulating materials and conductive materials may also be usedin place of those specifically mentioned. The application of the`devices illustrated is not limited to telemetering systems asspecifically discussed, but may be used in numerous different typesystems involving switching or sampling operations. Also, the switchingdevice disclosed may be employed in decommutation systems as well asother systems requiring the use of a switch functioning in the mannerdescribed.

What is claimed is:

l. A switching device comprising a brush holder, a plurality of brushesdisposed within said brush holder, a cylindrical member movable withrespect to said brush holder, a plurality of segmented contactsextending circumferentially about the periphery of said cylindricalmember, means for electrically connecting said plurality of contacts toeach other, said brushes and contacts extending along the length of saidcylindrical member and being aligned with respect to each other so thatone brush engages a corresponding contact when said cylindrical memberis moved, means for moving said cylindrical member to cause saidcontacts to sequentially engage said brushes, said plurality of contactsand said plurality of brushes being angularly disposed with respect toeach other whereby only one of said brushes sewage@ 7 8 engages one' ofsaid contacts at one time for each revolu- 1,110,676 Flint Sep. 15, 1914`ion of said cylindrical member. 1,311,437 Conklin July 29, 1919 2. Aswitching device as set forth in claim 1 wherein 1,343,141 Kenagy June8, 1920 means are provided for electricaHy connecting said p1ura1i-1,731,513 Wagner Oct. 15, 1929 ty of segmented contacs to each other. 52,167,750 Hale Aug. 1, 1939 2,496,621 Reed Jan. 31, 1950 ReferencesCited in the 111e of this patent 218521628 Fry Sept 16 1958 UNITEDSTATES PATENTS FOREIGN PATENTS

1. A SWITCHING DEVICE COMPRISING A BRUSH HOLDER, A PLURALITY OF BRUSHESDISPOSED WITHIN SAID BRUSH HOLDER, A CYLINDRICAL MEMBER MOVABLE WITHRESPECT TO SAID BRUSH HOLDER, A PLURALITY OF SEGMENTED CONTACTSEXTENDING CIRCUMFERENTIALLY ABOUT THE PERIPHERY OF SAID CYLINDRICALMEMBER, MEANS FOR ELECTRICALLY CONNECTING SAID PLURALITY OF CONTACTS TOEACH OTHER, SAID BRUSHES AND CONTACTS EXTENDING ALONG THE LENGTH OF SAIDCYLINDRICAL MEMBER AND BEING ALIGNED WITH RESPECT TO EACH OTHER SO THATONE BRUSH ENGAGES A CORRESPONDING CONTACT WHEN SAID CYLINDRICAL MEMBERIS MOVED, MEANS FOR MOVING SAID CYLINDRICAL MEMBER TO CAUSE SAIDCONTACTS TO SEQUENTIALLY ENGAGE SAID BRUSHES, SAID PLURALITY OF CONTACTSAND SAID PLURALITY OF BRUSHES BEING ANGULARLY DISPOSED WITH RESPECT TOEACH OTHER WHEREBY ONLY ONE OF SAID BRUSHES ENGAGES ONE OF SAID CONTACTSAT ONE TIME FOR EACH REVOLUTION OF SAID CYLINDRICAL MEMBER.